This application claims the priority of Japanese Patent Application No. 11-344842 filed Dec. 3, 1999, and Japanese Patent Application No. 2000-77876 filed Mar. 21, 2000.
1. Field of the Invention
The present invention relates to a linear transmission member driving unit for an endoscope, and more particularly to a driving unit for rotating a linear transmission member for changing an observation distance (including also changing depth of field) by a motor.
2. Description of the Prior Art
FIGS. 13A to 13C show a configuration of an endoscope (scope) to which a mechanism for making the observation distance (or depth of field) variable is applied, and FIG. 13A shows an endoscope operating unit 1A, and on the left side of this operating unit 1A, there are disposed an insertion unit 1B shown in FIG. 13B, and a tip end portion (hard portion) 1C shown in FIG. 13C. In this respect, the insertion unit 1B consists of the tip end portion 1C, an angle portion 1D and a soft portion 1E. Behind the operating unit 1A, there are disposed an air-supply/water-supply operating button 2A, a suction operating button 2B, a freeze switch 3A, other switches 3B and 3C, and an observation distance-variable switch 4 or the like.
Also, within the operating unit 1A, a motor 7 is mounted onto a chassis (base) 6 by a holding member 8, and a linear transmission member 10 formed of a multiple coiled spring is mounted to this motor 7 through a shaft connector 11. This linear transmission member 10 is placed within a flexible protective tube (soft tube) 12 in order to avoid any interference with other members, and this protective tube 12 is mounted to the chassis 6 with the holding member 13. These linear transmission member 10 and protective tube 12 are disposed from the operating unit 1A to the tip end portion 1C through the insertion unit 1B.
At the tip end portion 1C, there are disposed, as shown in FIG. 13C, an object lens 15, a movable lens 16 and a prism 17, and a CCD 18, which is a solid state imaging device, is optically connected below this prism 17. A holding member 19 of the movable lens 16 has a female threaded portion on top thereof, and on this female threaded portion, there is disposed a rotary driving member 20 whose male screwed portion threadably engages with this female threaded portion, and the linear transmission member 10 is coupled to the rotary driving member 20.
According to such a configuration, rotation of the motor 7 is transmitted to the rotary driving member 20 at the tip end portion 1C through the linear transmission member 10, and the rotary motion of this rotary driving member 20 is converted into a linear motion by means of threaded engagement with the holding member 19. This enables the movable lens 16 to move back and forth, making it possible to make an observation distance to be set in the objective optical system variable.
In an endoscope having the above described linear transmission member driving unit, when an angle portion 1D of the insertion unit 1B is curved as shown in FIG. 13B, the protective tube 12 advances and retreats by a length of, for example, L1, and the linear transmission member 10 advances and retreats by a length of, for example, L2 in a rotating shaft direction. More specifically, on focusing attention on a certain point P on the protective tube 12, it moves forward (toward a position P1) by a length L1 when the angle portion 1D is bent from a straight state. Since both end portions of the protective tube 12 are fixed to the neighborhood of its tip end portion 1C and the holding member 13, when the insertion unit 1B is set to a just suitable length in a straight state, the protective tube 12 is pulled during the bending operation, and as a result, the tip end portion 1C is deviated from a desired operating direction and tilts, so-called xe2x80x9ccrooked neckxe2x80x9d occurs. Thus, conventionally, the length of the protective tube 12 has been made a little longer than the armored body, and when it is being bent, the scope insertion unit 1B is disposed so as to push it into the protective tube 12.
On the other hand, one end of the linear transmission member 10 is connected to the rotary driving member 20, and is enveloped in the protective tube 12, and therefore, when the angle 1D is bent, the linear transmission member 10 moves backward (from position P to P2) by, for example, length L2. For this reason, there occurs an inconvenience that the linear transmission member 10 gives a load caused by pressure to the output shaft of the motor 7, and a change in posture of the insertion unit 1B changes the moving speed of the movable lens 16, that is, the magnification changing time. Thus, the linear transmission member 10 is mounted with reference to the time during the bending operation of the insertion unit 1B (during the maximum movement toward the motor side), and when the insertion unit 1B is made straight, a moderate pulling force is caused by a multiple coiled spring (linear transmission member 10) which expands and contracts so as to cause any load of the pressure not to be applied to the motor output shaft.
Since, however, the degree of expansion and contraction of the multiple coiled spring, which is the linear transmission member 10, changes depending upon bending (change in posture) of the insertion unit 1B including the angle portion 1D even in the above described configuration, the load to the motor output shaft cannot be maintained constant, leading to a problem that the posture of the insertion unit 1B causes variations in the magnification changing operation (operation of variable power).
Also, the angle portion 1D configuring the endoscope is used to point a tip hard portion 1C toward a desired direction, and is constructed so as to be curved by remote control from an angle operating device provided on the body operating unit 1A. This angle portion 1D is curved in order to mainly change the observation visual field of the endoscope. The insertion unit 1B is inserted into a narrow body cavity in order to perform inspection and diagnosis, and the overall length of the angle portion 1D is desirably made as short as possible in order to smoothly and reliably change the observation visual field even in the narrow body cavity or the like. Moreover, in order not to cause any dead angle in the observation visual field as far as possible, the angle of curvature must be made as large as possible. Accordingly, when the angle portion 1D is curved to the maximum angle of curvature, the radius of curvature is exceedingly small, and yet it is configured to be able to be abruptly curved such as, for example, 180xc2x0 or an angle of its vicinity. Also, since an insertion course within the body cavity has a complicatedly curved shape, the soft portion 1E coupled to the angle portion 1D has flexibility in a curved direction, and this soft portion is constructed so as to be able to be curved in any direction by following the curved insertion course.
The angle portion 1D is constructed so as to be curved larger than the soft portion 1E, and even in the protective tube 12 to be disposed within these, the inside of the angle portion 1D is curved larger so that the soft protective tube 12 becomes deformed as if it were crushed. Therefore, within this angle portion 1D, the frictional resistance of the linear transmission member 10 and the protective tube 12 becomes larger than the soft portion 1E, resulting in irregularity of the rotary driving-force of the linear transmission member 10, and there is a problem that the driving force lowers.
Further, in a state in which the angle portion 1D has been curved to the maximum, the protective tube 12 may become deformed so as to become flat, but since the linear transmission member on the one hand has high rigidity, and a change in the sectional shape is small, the linear transmission member 10 goes into a state in which the linear transmission member 10 is pressed into contact with the protective tube 12. Thus, when the linear transmission member 10 is caused to be rotated in this state, there is a problem that the frictional resistance due to rotation becomes large, resulting in a greater motor load.
The present invention has been achieved in the light of the above described problems, and is aimed to provide a linear transmission member driving unit for an endoscope capable of improving the transmission efficiency of a rotary driving force of the linear transmission member, reducing the load onto the motor, and maintaining operations such as magnification changing constant even if there may be a change in the posture of the endoscope insertion unit.
In order to attain the above described object, a linear transmission member driving unit for an endoscope according to the present invention is provided with: a linear transmission member which performs a rotary motion in order to drive an object; a protective tube which rotationally envelops this linear transmission member; a motor, to which the linear transmission member is shaft-connected; a chassis to which this motor is fixed; and a mobile type linear transmission member shaft coupling mechanism, which couples the shaft of the motor fixed to this chassis to an end portion of the linear transmission member, and to which this linear transmission member is mounted so as to be able to move in a direction of the rotating shaft of the motor.
The mobile type linear transmission member shaft coupling mechanism consists of a cylindrical member coupled and fixed to the motor shaft, and comprises: a shaft connecting member in which a sliding guide hole having a predetermined length in the direction of the rotating shaft is formed; and a distal member of the linear transmission member, which is disposed so as to move within a cylinder of this shaft connecting member, and, in which there is provided a pin for engaging with the sliding guide hole to slide, and a pin of this distal member is caused to be engaged with the sliding guide hole, whereby it is made possible to transmit rotation of the motor to the linear transmission member and to move the linear transmission member concerned in the direction of the rotating shaft by a predetermined amount.
According to the above described invention, it becomes possible for the distal member of the linear transmission member to move in the direction of the rotating shaft by the length of the sliding guide hole within the cylinder of the shaft connecting member, and this linear transmission member advances or retreats in the direction of the rotating shaft in response to the angle bending operation, and therefore, the linear transmission member consisting of a multiple coiled spring or the like does not expand nor contract any longer (even if it expands or contracts, its degree becomes small), but the load to be applied to the motor rotating shaft becomes substantially constant. Therefore, even if the insertion unit changes its posture, the magnification changing operation or the like can be executed by the stable rotary driving force.
In addition, the motor and the mobile type linear transmission member shaft coupling mechanism are disposed in space on the side of an angle operating knob mechanism being mounted, partitioned by the chassis within an operating unit, and the motor and the protective tube can be mounted to the chassis concerned by the use of an integrally formed holding member. Thereby, the space can be efficiently utilized, and any interference of the motor and the mobile type linear transmission member shaft coupling mechanism with various contents within the operating unit can be avoided. In other words, within the displacement space at a side opposite to the angle operating knob mechanism partitioned by the central chassis within the operating unit, there are disposed contents such as various conduit lines, light guides, and signal lines, and if the driving mechanism were disposed here, there would be such inconvenience that damage or the like to the contents occurs due to the interference. Thus, the influence on such contents can be avoided. Also, it becomes easy to position such that the motor driving shaft coincides with the central position of the protective tube.
Further, if as the above described chassis, a plurality of sheets of plates are superposedly disposed, it will be possible to mount the rotating shaft for the angle operating knob and the holding member onto different plates respectively, and in this case, there is an advantage that it becomes difficult for vibration during rotation of the motor to transmit to the angle operating knob.
It is preferable to apply lubricating coat to the sliding member of the mobile type shaft coupling mechanism, and in this case, it is capable of securing a smooth sliding operation by the lubricating coat, and improving the abrasion resistance.
On the outer periphery of the distal member, there are formed protruding portions in contact with the inner wall of the shaft connecting member at two positions where the pin is sandwiched therebetween such that the linear transmission member can be moved by sliding of these protruding portions within the shaft connecting member concerned. Thereby, it is possible to realize a smooth moving operation of the linear transmission member without the distal member tilting from the motor shaft direction (while maintaining parallelism) even though a force for tilting (falling) in a direction perpendicular to the moving direction may be exertedon the linear transmission member and the distal member.
A linear transmission member driving unit for an endoscope according to another invention is provided with: a movable member disposed on the side of the tip end of an insertion unit having an angle portion and a soft portion; a transmission coil comprising wire spirally wound, which is a linear transmission member for transmitting the rotary driving force of the motor to this movable member; and a flexible protective tube which rotationally envelops this transmission coil. The transmission coil, whose wire diameters are actually the same, consists of two coil portions having different outside diameters, and has a small-diameter coil portion having smaller outside diameter within the angle portion, and a large-diameter coil portion having larger outside diameter within the soft portion. These both coil portions are coupled by a coupling member so as to be able to integrally rotate at a connecting position between the angle portion and the soft portion or in the vicinity thereof.
The outside diameter of the small-diameter coil portion is preferably set so as to be smaller than the size in the direction of the end shaft when the angle portion goes into a maximum curved state and the protective tube becomes deformed so as to be flattened. According to this another invention, it becomes possible to efficiently transmit the rotary driving force by reducing the frictional resistance.